Field of the Invention
The present invention relates to the operation of photovoltaic power plants. More particularly, the present invention relates to methods, computer program products, controllers and systems for forecasting fluctuations in irradiance over a photovoltaic power plant due to cloud cover and enacting measures at the photovoltaic power plant in response to the forecasted fluctuations.
Description of Related Art
Renewable energy sources like solar power plants are subject to unpredictable power output due to changes in the environment in their vicinity. Chief among these are the movement of clouds which can rapidly cause their power output to fluctuate. As the percentage of power from such plants supplied to the public power grid increases the severity of the problem also increases. Recently power utilities are demanding that new solar power plants be designed with features to prevent their output from changing faster than a specified rate. Inadequate measures to address this issue can result in rapid voltage fluctuations in power grids that may produce a phenomenon known as “flicker”—rapid noticeable changes of energy being supplied, such as rapid visible changes in the light level provided by lighting equipment.
There are two methods to meet these new requirements. The first and most common approach is to include some type of energy storage or generation capability within the scope of the power plant. These include battery systems or diesel generators which can supplement the power produced by the plant when cloud events occur such that the power out remains within the required specifications sets. While technically straight forward this approach severely affects the economic viability of the project due to the high cost of batteries or resistance to application of diesel generators.
The second and less common approach is to forecast weather in such a way that the output of the plant can be gradually changed in advance of when cloud cover would appear. Approaches that have been attempted include mounting sensors around the periphery of the plant or in locations remote from the plant in an attempt to predict when cloud cover is imminent. The problem with this approach is that sensors near the plant cannot give enough advance notice and sensors remote from the plant would be expensive to install and difficult to communicate with.
Various efforts have been made to address this issue or factors related to this issue, including those described in U.S. Pat. Nos. 4,491,727; 6,133,990; 4,355,896; 7,414,706; 8,369,999; and 8,437,959; and International Patent Application Publication Nos. WO 2011/017323 A1; WO 2011/124720 A1; WO 2011/152448 A1; WO 2012/146618 A1; WO 2011/129473 A1; WO 2007/047048 A1; and WO 2013/124421 A1; and US Patent Application Publication Nos. 2010/0198420 A1; 2004/0135989 A1; 2005/0175253 A1; 2007/0084502 A1; and 2011/0276269 A1; as well as Japanese Patent Application Publication Nos. JP 2007184354 A; JP 2010186840 A; JP 2009252950 A; JP 2011159199 A; JP S60220843 A; as well as Chinese Patent Application Publication Nos. CN 102915470 A; CN 101969207 A; CN 102244483 A; CN 201104273 Y; CN 103116711 A; as well as Spanish Patent Application Publication No. 2257914 A1. However, despite these efforts, there still remains a need in the art to forecast power fluctuations at photovoltaic power plants caused by cloud phenomenon.